Ever heard of sleep drunkenness? Well, this is a sleep disorder that may be as prevalent as affecting one in every seven people, new research says.

Sleep drunkenness disorder involves confusion or inappropriate behaviour such as answering the phone instead of turning off the alarm, during or following arousal from sleep, either during the first part of the night or in the morning.

An episode, often triggered by a forced awakening, may even cause violent behaviour.

“These episodes of waking up confused have received considerably less attention than sleepwalking even though the consequences can be just as serious,” said study author Maurice M Ohayon from Stanford University’s school of medicine.

For the study, 19,136 people aged 18 and older were interviewed about their sleep habits and whether they had experienced any symptoms of the disorder.

Participants were also asked about mental illness diagnoses and any medications they took.

The study found that 15 percent of the group had experienced an episode in the last year, with more than half reporting more than one episode per week.

In the majority of cases – 84 percent – people with sleep drunkenness also had a sleep disorder, a mental health disorder or were taking psychotropic drugs such as antidepressants.

Less than 1 percent of the people with sleep drunkenness had no known cause or related condition.

Among those who had an episode, 37.4 percent also had a mental disorder.